ADESBA - A new general global control system applied to the ...

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12 th International Conference on Urban Drainage, Porto Alegre/Brazil, 11-16 September 2011 Since 2007, the Hildesheim urban drainage department implements a step-wise optimisation of the throttle settings. In a further step in 2010, with the implementation of the RTC system, the dynamic control of the storm-water overflow tanks was further optimised. For this purpose, on the basis of the KOSIM model, first of all, a hydrological sewer network model was set up in SIMBA, thus allowing to simulate and to analyse the control algorithms in a very flexible way. The model was calibrated and verified. Figure 2 presents a comparison between the simulated and the measured wastewater treatment plant inflows. Figure 2. Results from verification at the inflow of WWTP of Hildesheim In this period (23.7.-3.8.2007) 450,681 m³ of wastewater flowed into the WWTP. Due to infiltration water flows from the catchments with separate sewer networks, the simulation results matches the inflow data roughly by 93%. If the results are compared separately only for the part of the combined sewer catchments the difference amounts to only 1%. Examples of changes in the disposal of surplus quantities of storm sewage brought about in the 23.7.-3.8.2007 period can be taken from Table 1 (cf Figure 2). As at this time operation of the throttle discharges involved stationary optimisation at 4 tanks, this variant is also shown. Table 1. Simulated CSO discharges during the period 23.7. - 3.8.2007 CSO (m³) Stationary throttle ADESBA-control box without opti- with optimization at 4 tanks 9 tanks mization 4 tanks Mastbergstr. 208 301 301 0 Cheruskerring 3.187 2.397 2.397 2.347 Speicherstr. 801 907 907 318 Schützenallee 9.196 7.251 6.123 6.731 Alter Markt 2.124 2.124 2.124 305 Treibestr. 3.966 3.966 2.347 2.612 Hohnsen 4.169 4.169 2.413 2.514 Lönsbruch 537 537 537 156 Tank WWTP 0 0 0 20 Total 24.188 21.652 17.149 15.003 Reduction 10,5 % 29,1 % 38,0 % Maximum use of Tank WWTP 34 % 38 % 84 % 100 % 4 ADESBA - A new general global control system
12 th International Conference on Urban Drainage, Porto Alegre/Brazil, 11-16 September 2011 The results show a considerable reduction in the quantities of CSO due to the use of the RTC system. Analysing the maximum utilisation of the stormwater tank capacity in the treatment plant, the basic principle of uniform utilisation of storage capacities becomes clear. This increases from below 40% in the case of stationary throttle settings to 100% in the case of RTC system control of nine tanks. Confirmation of this basic suitability of the control algorithm is given in Table 2 in the form of a long-term simulation and the proof of pollutant load reduction. Table 2. CSO discharges of long-term simulation (10 years) Uniform rainfall With virtual non-uniform rainfall Stationary throttle ADESBA-control box without optimization 4 tanks 9 tanks 4 tanks 9 tanks CSO (m³/a) 171.632 123.888 121.761 120.171 117.444 Reduction 28 % 29 % 30 % 32 % CSO load (kg CSB/a) 19.625 14.233 14.111 13.788 13.569 Reduction 27 % 28 % 30 % 31 % The long-term simulation (10 years) for verifying the load reduction showed a considerable reduction in storm water discharges (29 percent) compared to stationary operation. Compared to the maximum control potential based on the central basin approach (DWA, 2005), the degree of ADESBA control system efficiency, assuming uniform distribution of rainfall, amounts to 82% relative to the amount discharged (for RTC of 9 tanks) and to 92% for RTC of 4 tanks. Simulation studies with non-uniformly rainfall show that the real control potential of ADESBA is even higher. Additional optimisation potential emerges from the possibility of prioritising the various tanks, especially with a view to minimising the pollutant load of CSO (Lacour and Schütze, 2010). DEVELOPMENT AND DEPLOYMENT OF THE ADESBA RTC MODULE AT HILDESHEIM The ADESBA RTC system box (hardware) was developed by SEGNO company. To enable the maximum number of sewage system operators to have equipment compatible with existing systems, standard technologies were used when selecting hardware and software components. As the PLC family, Panasonic products were envisaged, as the latter provide optimum support for the standard version of IEC61131-3 Structured Text. However, in the course of the project, customers required the use of Siemens control units with a view to permitting the use of existing resources by the municipality of Hildesheim. For this purpose, the algorithm created by ifak in the standard IEC61131-3 Structured Text version had to be additionally adapted to the Siemens Structured Text version. The rapid and uncomplicated adaptation of the control algorithm demonstrates the advantages of the SIMBA simulation environment, as described above. Moreover, a test of the RTC module performed in the course of the project showed that it can be completely adapted to standard, commerciallyavailable programmable logic controllers (Peikert et al., 2010). The module is designed to be used as a local control unit in standalone mode as well as for the use of RTC system. For this purpose, intercommunication between the various modules has to be assured. At Hildesheim, numerous structures are installed in a subterranean fashion so that Pabst et al. 5
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